1. Field of the Invention
The present invention relates to a disc medium accommodating case and, in particular, to a disc medium accommodating case for accommodating and transferring a large number of disc media, for example, a plurality of optical discs such as CD-R (compact disc recordable) and DVD (digital video disc).
2. Description of the Related Art
The conventional music CDs (CD-ROM; compact disc read only memory) sold at record shops, etc. are media for reading only; information is recorded in the pressing process, so that writing of new information is impossible.
The disc media that are on sale under the abbreviated designation of "CD-R" are so-called "write-once" type media, which allow information to be written thereto only once. CD-R are shipped in a blank condition like blank tapes and discs, so that the user can record various kinds of information thereon, making it possible to easily and economically produce CDs.
As shown in FIG. 17, a CD-R 10 usually comprises four layers superimposed one upon the other in the following order: a transparent synthetic resin substrate 12 formed of polycarbonate or the like and having 1.6 .mu.m pitch guide grooves 11; a pigment recording layer 13; a metal reflection layer 14; and a UV resin top coating layer 15.
To perform recording on this CD-R 10, constructed as described above, information is written thereto by applying laser pulses condensed on the guide grooves 11 formed on the disc substrate. The bits, the units for recording, are formed by generating deformed portions (recording pits) in the order of sub-micron on the disc substrate through mutual action between the pigment heated and melted by the laser application to partially decompose and the substrate material softened by heating. Thus, a recording medium having a very stable structure is obtained.
Regarding the equipment for performing recording on the CD-R 10, having the above features, no conventional equipment for performing recording on CDs, such as equipment for complicated data processing or equipment for large-scale cutting or stamping, is required. That is, to perform recording on the CD-R 10, the above-described processing for recording on CD is not necessary, and data can be written easily by a CD recording unit, whereby the production is executed in a relatively small equipment. On the UV resin top coating layer 15 of the CD-R 10 on which data has been written, printing is performed by silk printing or the like to protect the recorded information, etc.
In this way, when producing the CD-R 10, unrecorded disc media are prepared in relatively large-scale, well-managed plant, and then a plurality of them are accommodated in a disc medium accommodating case called bulk pack before they are transferred to a relatively small-scale production company for writing information, where the recording of information, the printing of labels, etc. are performed; the disc media are then accommodated in CD carrying cases or the like and sold or distributed.
As shown in FIG. 18, a disc medium accommodating case 20 for accommodating a large number of disc media, such as CD-R, for conveyance is generally formed as a truncated cone and comprises a case bottom plate member 21 having a diameter larger than the outer diameter of a CD-R (hereinafter referred to as the disc medium), a stacking column 22 arranged in an erect position at the center of this case bottom plate member 21, a protective cover member 23 formed as a truncated cone and adapted to be placed on the case bottom plate member 21, and a cap 24 for securing this protective cover member 23 in position through the intermediation of the stacking column 22.
As shown in FIG. 19, at the center of the case bottom plate member 21, there is provided a female screw portion 25 for keeping the stacking column 22 erect.
As shown in FIG. 18, the stacking column 22 includes a column portion 27 having a diameter smaller than the inner diameter of the chucking hole 26 of the disc medium 10 and having at its forward end a male screw to form a male threaded-engagement portion 28. At the base end thereof, there is provided a male screw portion 29 (See FIG. 19) adapted to be threadedly engaged with a female screw portion 25 of the case bottom plate member 21.
The protective cover member 23, which is formed as a truncated cone, includes a top surface 30 whose diameter is larger than the outer diameter of the disc medium 10. The bottom portion of the protective cover, which is connected to the top surface 30 through the intermediation of a peripheral side wall 31, has a diameter that fits to the outer diameter of the case bottom plate member 21. At the center of the top surface 30, there is provided a through-hole 32 which engages with some play with the male threaded-engagement portion 28 of the stacking column 22.
The cap 24 is formed as a cylinder; at the center of the bottom portion thereof, there is provided a female threaded-engagement portion 33 consisting of a female screw adapted to threadedly engage with the male threaded-engagement portion 28 of the stacking column 22.
In the disc medium accommodating case 20, constructed as described above, a plurality of disc media 10 are first fitted onto the column portion 27 of the stacking column 22 by inserting column portion through the chucking holes 26 of the disc media 10. After a desired number of disc media 10 have been mounted, the protective cover 23 is placed thereon from above. At this time, the through-hole 32 is engaged with the male threaded-engagement portion 28, and then the outer peripheral end portion at the bottom of the protective cover 23 is fitted onto the outer peripheral portion of the case bottom plate member 21. In this condition, the cap 24 is fitted from above onto the male threaded-engagement portion 28 of the stacking column 22, and turned to in the closing direction, whereby the case is completed. In this way, the disc media 10 is accommodated for transportation.
However, in the above construction, to engage the stacking column with the disc-like case plate member, the male screw portion of the stacking column is threadedly engaged with the female screw portion of the case bottom plate member. Due to this construction, there is a fear that the male and female screw portions will be deflected, broken, etc. due to the vibrations and impact when a large number of disc media are mounted and transported.
To solve this problem, an adhesive is poured into the treaded-engagement portion where the male screw portion of the stacking column is threadedly engaged with the female screw portion of the case bottom plate member to thereby achieve reinforcement.
However, the reinforcement with an adhesive or the like has a problem in that trace amounts of the out gas generated when the adhesive cures has an adverse effect on the accommodated disc media (CD-R). Thus, the curing is conducted for a long period of time before accommodating the disc media, which means it is necessary to secure the space for placing the case. Further, the case cannot be used until the curing is complete, so that the process time cannot be reduced.